On Aug. 10, 1897, German chemist Felix Hoffmann searching for something to relieve his father’s arthritis synthesized acetylsalicylic acid (ASA) aspirin and heroin, and Bayer began to market the substance as Aspirin. Acetylsalicylic acid was originally made from a chemical found in the bark of willow trees.

Felix Hoffmann is generally recognized for the creating the first synthesized medically forms of heroin and aspirin. However, this is disputed and others believe that Arthur Eichengrun was the real inventor.